Synthesis of Janus Rubber Hybrid Particles and Interfacial Behavior

Reactive Janus Particle Compatibilizer with Adjustable Structure and Optimal Interface Location for Compatibilization of Highly Immiscible Polymer Blends

Highly immiscible blend materials with distinctive and excellent properties play a key role in meeting the application needs, especially in extreme environments, and reactive nanoparticles are used to increase the interface adhesion and optimize the morphology of highly immiscible blending. However, these reactive nanoparticles tend to aggregate and even agglomerate during reactive blending, which significantly deteriorates their compatibilization efficiency. Herein, reactive Janus particles with the epoxy group and various siloxane molecular long chain grafting ratios (E-JP-PDMS) were synthesized using SiO₂@PDVB Janus particles (JP) and used as compatibilizers for polyamide and methyl vinyl silicone elastomer (PA/MVQ) blends, which were highly immiscible. The effects of the structure of E-JP-PDMS Janus nanoparticles on their location at the interfaces between the PA and MVQ as well as their compatibilization efficiency for the PA/MVQ blends were investigated. The location and dispersion of E-JP-PDMS at the interfaces were improved by increasing the PDMS content in E-JP-PDMS. The average diameter of the MVQ domains of the PA/MVQ (70/30, w/w) was 79.5 μm and was reduced to 5.3 μm in the presence of 3.0 wt % of the E-JP-PDMS with 65 wt % PDMS. As a comparison, it was 45.1 μm in the presence of 3.0 wt % of a commercial compatibilizer (ethylene-butylacylate-maleic anhydride copolymer, denoted as EBAMAH), which provides a guideline for the design and preparation of efficient compatibilizers for highly immiscible polymer blends.

Poly(lactic acid)/Poly(butylene succinate) (PLA/PBS) Layered Composite Gas Barrier Membranes by Anisotropic Janus Nanosheets Compartibilizers

Poly(lactic acid) (PLA), one of the most promising biodegradable polymer products, has achieved wide applications for its relatively good mechanical properties and moderate degradability. Here we report an environment-friendly filler, the organic-inorganic composite Janus nanosheets (PLA/PBS JNs), which can jam at the interface of the PLA/PBS blend with a low threshold as the compatibilizer and can simultaneously toughen the composites and improve the gas barrier performance due to better interfacial interaction and tortuous path effect. With 0.3 wt % of PLA/PBS JNs added, the tensile strength and elongation at break of the PLA/PBS blend can be improved by 37% and 224%, respectively. After a further hot-pressing process, the barrier performance of the PLA/PBS composite membranes can be significantly enhanced since PLA, PLA/PBS JNs, and PBS are arranged in a nearly lamellar structure with oxygen permeability of 0.63 × 10^-15 cm³ cm·cm^-2 s^-1 Pa^-1 with only 0.5 wt % of PLA/PBS JNs.

Facile synthesis of micron-size Janus particles by one-pot suspension polymerization and their functional modification

A novel strategy for preparing micron-size Janus particles with easily-functionalized surfaces was established by one-pot W/O/W-type suspension polymerization for the first time.

Stabilizing Polymeric Interface by Janus Nanosheet

A strategy is proposed to stabilize the polymeric interface by using the irregular Janus nanosheet (JNS). The poly(vinylidene fluoride) (PVDF)/poly(l-lactic acid) (PLLA) at 60/40 (wt/wt) with a bi-continuous structure is selected as the model melt blend, and the PMMA/epoxy JNS is synthesized and used as the compatibilizer. The JNS is preferentially located at the interface. The interfacial coverage by the JNS reaches a saturated state forming the interconnected jamming structure at 0.5 wt% of the JNS. The interface is thus stabilized which is well preserved after annealing at high temperature. After selectively etching PLLA, the robust PVDF porous material is derived with the JNS armored at the pore skeleton surface. The porous material provides a universal scaffold to achieve stable functional materials after filling the pores.

Interfacial aggregation of Janus rods in binary polymer blends and their effect on phase separation

Janus particles interfacially self-assemble into different structures when incorporated into multiphase systems. Dissipative particle dynamics simulations are employed herein to investigate the interplay between aggregation mechanisms and phase separation in polymer blends. Shorter rods with a standing configuration become increasingly "caged" or trapped in larger aggregates as weight fraction increases, which is reflected in the way that their diffusion is coupled to their aggregation rates. Janus rods of higher aspect ratios that are tilted at the interface aggregate side-by-side and are able to hinder phase separation kinetics. This is due to a combination of individual Janus rod conformations at the interface, their intrinsic aggregation mechanisms, aggregate fractal dimension, and aggregation rates, and can also be traced back to the scaling of the diffusion coefficient of aggregates with their size. Findings presented provide insight into the mechanisms governing two dimensionally growing colloidal aggregates at fluid interfaces, more specifically, those associated with Janus particles, and shed light on the potential of these systems in paving the way for designing new functional materials.

Co-assembly of Janus nanoparticles in block copolymer systems

Block copolymer are ideal matrices to control the localisation of colloids. Furthermore, anisotropic nanoparticles such as Janus nanoparticles possess an additional orientational degree of freedom that can play a crucial role in the formation of highly ordered materials made of block copolymers. This work presents a mesoscopic simulation method to assert the co-assembly of Janus nanoparticles in a block copolymer mixture, finding numerous instances of aggregation and formation of ordered configurations. Comparison with chemically homogeneous neutral nanoparticles shows that Janus nanoparticles are less prone to induce bridging along lamellar domains, thus being a less destructive way to segregate nanoparticles at interfaces. The combination of asymmetric block copolymer and asymmetric Janus nanoparticles can result in assembly of colloids with an even number of layers within the minority domain.

Amphiphilic Janus nanosheets by grafting reactive rubber brushes for reinforced rubber materials

An amphiphilic Janus nanosheet with different reactive rubber brushes on two opposite sides can simultaneously strengthen and toughen rubber blends.

Onset Reduction and Stabilization of Cocontinuous Morphology in Immiscible Polymer Blends by Snowmanlike Janus Nanoparticles

Interfacial jamming of monolayer nanoparticles is often required to kinetically arrest the cocontinuous morphology, which is not in favor of achieving high efficiency at low particle contents. In this paper, we find that the shape asymmetry of the snowmanlike Janus particles (JPs) has significant influence on the cocontinuous morphology of polymer blends under the melt-mixing process. The addition of 0.9 vol % snowmanlike JPs can almost have the onset concentration of cocontinuity in immiscible blends, which is much lower than the apparent interfacial jamming concentration. In addition, JPs show superior ability to stabilize the continuous morphology during annealing at high temperatures. The interfacial activity of asymmetric JPs is due to the decrease in the radius of the jamming curvature in the interfacial region as the shape asymmetry of the snowmanlike JPs increases. This result implies a general strategy to prepare Janus nanoparticles for a highly effective interfacial modification agent at low contents, which can induce the dispersed-phase continuity and suppress the coarsening of cocontinuous morphology simultaneously.

Polymeric Janus Nanoparticles: Recent Advances in Synthetic Strategies, Materials Properties, and Applications

Polymeric Janus nanoparticles with two sides of incompatible chemistry have received increasing attention due to their tunable asymmetric structure and unique material characteristics. Recently, with the rapid progress in controlled polymerization combined with novel fabrication techniques, a large array of functional polymeric Janus particles are diversified with sophisticated architecture and applications. In this review, the most recently developed strategies for controlled synthesis of polymeric Janus nanoparticles with well-defined size and complex superstructures are summarized. In addition, the pros and cons of each approach in mediating the anisotropic shapes of polymeric Janus particles as well as their asymmetric spatial distribution of chemical compositions and functionalities are discussed and compared. Finally, these newly developed structural nanoparticles with specific shapes and surface functions orientated applications in different domains are also discussed, followed by the perspectives and challenges faced in the further advancement of polymeric Janus nanoparticles as high performance materials.

Janus Colloids toward Interfacial Engineering

Janus colloids are functional particles consisting of two surfaces (or internal materials) with distinct physical or chemical properties in the same particle. Owing to their amphiphilic nature, Janus colloids composed of both hydrophilic and hydrophobic faces provide a powerful tool to generate functional surfaces and to manipulate the properties of interfaces. Amphiphilic Janus colloids have shown promising applications as particulate surfactants in oil/water separation, as interfacial compatibilizers in polymer blends, and as assembly blocks in robust coatings with unique wettability. In this Feature Article, we summarize recent advances in engineering interfaces by using Janus colloids.

Janus Nanoparticles for Improved Dentin Bonding

The amphiphilic monomer 2-hydroxyethyl methacrylate (HEMA) is widely used in dental adhesives as a priming component, especially for dentin bonding. It behaves as a compatibilizer between hydrophilic and hydrophobic components and stabilizes the multicomponent adhesive system. However, there are several drawbacks associated with using HEMA, such as water retention within the adhesive layer, hydrolysis in oral environments, and cytotoxicity. These drawbacks lead to the failure of tooth restoration and represent a heavy medical burden. Thus, it is imperative to find a new compatibilizer to substitute for HEMA. Because of their superior compatibilization capabilities as functional solid surfactants, amphiphilic Janus particles are chosen as candidates for an alternative to HEMA in dental adhesives. Reactive amphiphilic Janus nanoparticles are synthesized by selectively etching and modifying at the interface of a Pickering emulsion. This approach could be extended to the synthesis of a series of other Janus nanoparticles. The Janus nanoparticles were verified to be better for the reduction of the phase separation and stabilization of dentin adhesives than HEMA. It is also demonstrated that these reactive Janus nanoparticles can strongly enhance the dentin bonding interface without cytotoxicity. It is clearly illustrated by this study that Janus nanoparticles may be promising materials to substitute for HEMA in dental adhesives.

Reactive Nanoparticles Compatibilized Immiscible Polymer Blends: Synthesis of Reactive SiO2 with Long Poly(methyl methacrylate) Chains and the in Situ Formation of Janus SiO2 Nanoparticles Anchored Exclusively at the Interface

The exclusive location of compatibilizers at the interface of immiscible binary polymer blends to bridge the neighboring phases is the most important issue for fabricating desirable materials with synergistic properties. However, the positional stability of the compatibilizers at the interface remains a challenge in both scientific and technical points of view due to the intrinsic flexibility of compatibilizer molecules against aggressive processing conditions. Herein, taking the typical immiscible poly vinylidene fluoride (PVDF)/polylactic acid (PLLA) blend as an example, we demonstrate a novel approach, termed as the interfacial nanoparticle compatibilization (IPC) mechanism, to overcome the challenges by packing nanoparticles thermodynamically at the interface through melt reactive blending. Specifically, we have first synthesized nanosilica with both reactive epoxide groups and long poly(methyl methacrylate) (PMMA) tails, called reactive PMMA-graft-SiO₂ (Epoxy-MSiO₂), and then incorporated the Epoxy-MSiO₂ into the PVDF/PLLA (50/50, w/w) blends by melt blending. PLLA was in situ grafted onto SiO₂ by the reaction of the carboxylic acid groups with epoxide groups on the surface of SiO₂. Therefore, the reacted SiO₂ particles were exclusively located at the interface by the formation of the Janus-faced silica hybrid nanoparticles (JSNp) with pregrafted PMMA tails entangled with PVDF molecular chains in the PVDF phase and the in situ grafted PLLA chains embedded in the PLLA phase. Such JSNp with a distinct hemisphere, functioning as compatibilizer, can not only suppress coalescence of PVDF domains by its steric repulsion but also enhance interfacial adhesion via the selective interactions with the corresponding miscible phase. The interfacial location of JSNp is very stable even under the severe shear field and annealing in the melt. This IPC mechanism paves a new possibility to use the various types of nanoparticles as both effective compatibilizers and functional fillers for immiscible polymer blends.

Janus nanoparticles inside polymeric materials: interfacial arrangement toward functional hybrid materials

Recent advances and successes in interfacial behavior of Janus NPs at interfaces are summarized, with the hope to motivate additional efforts in the studies of Janus NPs in polymer matrix for the design of functional hybrid nanostructures and devices with engineered, desired and tailored properties for real-life applications.

Fast swelling strategy for flower-like micro-sized colloidal surfactants with controllable patches by regulating the Tg of seed particles

We are reporting an efficient fast swelling procedure by regulating the glass transition temperature T_g of poly(glycidyl methacrylate) (PGMA) seed particles via copolymerization with n-butyl acrylate (nBA).

Hybrid Hairy Janus Particles as Building Blocks for Antibiofouling Surfaces

Herein, we report a new strategy for the design of antifouling surfaces by using hybrid hairy Janus particles. The amphiphilic Janus particles possess either a spherical or a plateletlike shape and have core-shell structures with an inorganic core and hydrophilic/hydrophobic polymeric shells. Subsequently, these bifunctional Janus particles enable the fabrication of surfaces with modularity in chemical composition and final surface topography, which possess antifouling properties. The antifouling and fouling-release capability of the composite Janus particle-based surfaces is investigated using the marine biofilm-forming bacteria Cobetia marina. The Janus particle-based coatings are robust and significantly reduce bacterial retention under both static and dynamic conditions independent of the particle geometry. The plateletlike (kaolinite-based) Janus particles represent a scalable system for the rational design of antifouling coatings as well as their large-scale production and application in the future.